多配置波函数的离子特征的量化:诊断的Q
Silmar A do Monte1, Rene F K Spada2, Rodolpho L R Alves1
1Departamento de Química, CCEN, Universidade Federal da Paraíba, 58051-900 João Pessoa, Brazil.
完全活性空间自相一致场 (CASSCF) 方法可以在具有离子性质的分子的激发能量中产生很大的误差. 一个新的诊断器,Qt,预测这些错误,使得更多可靠的多引用量子化学计算.
科学领域:
- 量子化学 是一个量子化学.
- 计算化学的计算化学
- 频谱学是一种光谱学.
背景情况:
- 完整的活性空间自相一致场 (CASSCF) 是激发状态计算的基础.
- 最小活性空间CASSCF可以导致具有离子性质的状态的激发能量的显著误差 (>2 eV).
研究的目的:
- 引入一个新的诊断,Qt,以识别激发状态中的离子特征.
- 评估CASSCF在结合有机分子中的激发能量的准确性.
- 展示Qt在预测CASSCF错误中的实用性.
主要方法:
- 使用状态平均的CASSCF计算垂直激发能量.
- 基于过渡密度的Qt诊断的开发和应用.
- 与单个和双个激发和波普尔大小扩展性校正 (MR-CISD+P) 的多参考配置相互作用进行比较.
主要成果:
- 国家平均CASSCF显示34个单个州的平均绝对误差 (MAE) 为0.87 eV.
- 在CASSCF错误和Qt诊断之间观察到强烈的相关性.
- 在MR-CISD+P计算中,MAE为0.11 eV,结果很好,Qt相关性消失了.
结论:
- Qt诊断有效地预测了CASSCF计算中的有问题的情况.
- MR-CISD+P为激发能量的准确性提供了显著的改善.
- Qt诊断可以提高多引用计算的可靠性和用户友好性.
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